The invention relates to a window lifter for a vehicle door comprising a guide rail, a slider slidingly mounted on said rail and supporting a window glass, at least one branch of the cable passing over cable guiding or returning means provided at the ends of said rail and connecting said slider to a drive drum mounted on a side plate integral with said rail and means for tensioning at least one branch of said cable.
Correct operation of this so-called xe2x80x9ccable-operatedxe2x80x9d window lifter is ensured only if the cable is kept taught over its whole length.
If this is not the case, the absence of tension in the cable affects angular play in the window lifter crank. Insufficient tension in the cable can also lead to the cable escaping from the guides or channels provided in the cable guiding or returning means and incorrect winding in the channels provided on the drive drum.
The cable guiding or returning means generally consist of channels or grooves formed at the ends of the rail, the cable sliding therein, or peripheral grooves on direction-changing pulleys pivotally mounted on axes perpendicular to the plane formed by the cable branches.
Cable length is calculated to allow a slight operating slack, and to ensure the cable can be mounted when assembling the window lifter.
FR-A-2 733 292 provided a cable tensioning device comprising a cam rotatively mounted at one end of a rail and including an arm having a channel in which the cable slides, said cam being biased by a spring coaxial with said cam whereby the channel provided at the end of said arm exercises an outwardly-directed force on the said cable.
DE-A-3201098 provides a window lifter cable tensioning device comprising a cable return means mounted on a cam. The cam is biased by a curved helical spring.
These tensioning devices require the manufacturing and the assembly of at least two parts: the cam and the coaxial spring.
U.S. Pat. No. 4,235,046 provides a window lifter cable tensioning device comprising a deflecting element which engages and guides a cable in a loop-shaped path. A spring in a permanently stressed condition biases the deflecting element in a direction to lengthen the path of the cable.
This tensioning device requires a complicated spring and deflecting element assembly.
There is also a need for a window lifter providing a reduced assembly time and a reduced number of parts.
The window lifter according to the invention comprises a window slider, a cable driving said window slider, a spring having a mobile cable tensioning portion and having a fixed cable return portion, both portions engaging the cable.
In another embodiment, the window lifter further comprises a support plate having a cable return means, and wherein the fixed portion of the spring is engaged between the cable and the cable return means.
In a further embodiment, the window lifter the fixed spring cable return portion is attached to the cable return means.
In still another embodiment, the window lifter further comprises a tab fixed to the support plate and said return means comprises two flanges on both sides of the spring, said flanges having respective aligned slots through which the tab extends.
The spring mobile portion has preferably a cable guiding channel portion.
The fixed portion has preferably a cable guiding channel.
In a particular embodiment, the spring is a plate spring.
In an alternative embodiment the window lifter comprises a window slider, a cable driving said window slider and a wire spring having a fixed portion and a mobile cable tensioning portion having a loop through which the cable passes.
In another embodiment, the wire spring is located at the side of a cable return means and the spring fixed portion has a curved end that engages resiliently with the slider.
The loop can have an aperture adapted for inserting the cable in the loop.
The window lifter can also comprise a supporting plate having cable sheath stops, a drum mounted rotatably on the supporting plate, driving the cable, a slider guiding rail having two cable return means, separated from the supporting plate, and having cable sheath stops and cable sheaths surrounding the cable between respective rail cable sheath stops and supporting plate cable sheath stops.
The window lifter can also comprise a slider guiding rail having two cable return means at its ends and having a protruding plate, a drum mounted rotatably on the protruding plate and driving the cable.
The window lifter can also comprise a supporting plate having two cable sheath stops, two sliding guiding rails separated from the supporting plate, having respectively two cable return means and two cable sheath stops, and three cable sheaths surrounding the cable respectively between a first rail cable sheath stop and a first supporting plate cable sheath stop, between a second rail cable sheath stop and a second supporting plate cable sheath stop and between remaining cable sheath stops of the first and second rail.